A module has conventionally been used for storing and conveying fragile, heavy, rectangular thin panels, such as solar panels, in a manner that the panels are piled up vertically without contact.
Patent Document 1 discloses an example thereof.
This module includes: a supporting surface for supporting a rectangular thin panel from below; and a mold-product member connected to the supporting surface in a manner of extending outward from the supporting surface and vertically transmitting the weight of the rectangular thin panel. This module has a recess and a protrusion, which can be engaged with each other, on upper and lower parts of this mold-product member.
With such modules, it is possible to pile up the rectangular thin panels vertically without contact as follows: The modules are put on four corners of a rectangular thin panel with its periphery supported by a rectangular annular outer frame. Then, the rectangular thin panel is disposed on the supporting surface via the outer frame. Next, at each corner, the recess at the lower part of the mold-product member of another module is fitted to the protrusion at the upper part of the mold-product member of the module already disposed. Similarly, the next rectangular thin panel is supported by four modules. Without the outer frame, however, the modules cause the following program when the four corners of the rectangular thin panel are disposed on the supporting surface of each module. That is, the rectangular thin panel can be scratched or damaged during the conveyance.
More specifically, for example, the rectangular thin panel vibrates when: the piled rectangular thin panels are transported in a truck or the pallet runs on an uneven road. In the occurrence of such vibration, the substantially central part of the rectangular thin panel has the maximum amplitude vertically. Here, each corner part of the rectangular thin panel disposed on the supporting surface of the module is a free end. Therefore, as compared with the case where each corner part becomes a fixed end due to the use of an outer frame, the vibration at the central part of the rectangular thin panel tends to be amplified. As a result, due to the vibration of each corner part of the rectangular thin panel or due to the contact between each corner part of the rectangular thin panel and the upper and lower supporting parts, the rectangular thin panel may be scratched or, in some cases, damaged. In view of this, the insertion of a cushion spacer having a cushioning function with a predetermined size between a lower surface of the upper rectangular thin panel and an upper surface of the lower rectangular thin panel is suggested. This cushion spacer serves as an alternative to the modules disposed at the four corners of the rectangular thin panel when the rectangular thin panels are piled up. There are various configurations of the rectangular thin panel. For example, the upper surface of the solar panel is generally provided with a power distribution box and/or cord. On this occasion, a clearance is needed between the solar panels to be piled up on each other or the size of the cushion spacer needs to be restricted. The restriction of the size of the cushion spacer is to reduce the load receiving area of the rectangular thin panel. As this load receiving area is smaller (especially as the size of the cushion spacer located lower is restricted more), the rectangular thin panel is more easily crushed due to the increasing weight of the rectangular thin panel located above. Meanwhile, when the cushion spacers are vertically adjacent to each other via the piled rectangular thin panel, the upper cushion spacer can be moved relative to the lower cushion spacer in a long-side or short-side direction of the rectangular thin panel. In this case, it is difficult to stably position the rectangular thin panel supported by the cushion spacer. Therefore, for example, the load may be shifted due to the vibration during the conveyance, resulting in that the rectangular thin panel may be damaged. For this reason, it is necessary to restrict the relative movement between the cushion spacers adjacent to each other vertically. However, there is no choice but to provide such a positioning portion outside the rectangular thin panel, i.e., at a portion that does not receive the load of the rectangular thin panel. In this case, a shear force is generated vertically in the cushion spacer, specifically between the portion that receives the load of the rectangular thin panel and the portion that does not receive the load of the rectangular thin panel. This may result in that the structural integrity of the cushion spacer made of resin is degraded over time.
In this regard, Patent Document 2 discloses a housing unit for the rectangular thin panel utilizing such cushion spacers. More specifically, this conveyance unit forms one unit by alternately piling up a cushion member and a glass plate when housing the glass plates in a pallet. Here, the glass plate is a glass plate having a plurality of resin frames, which is a window glass for an automobile. The cushion member includes a self-adhesive member on a surface thereof that abuts on the glass plate. The unit is disposed on a bottom-receiving member formed on a bottom of the pallet via the cushion member having the self-adhesive member. Next, the cushion member including the self-adhesive member is disposed on an upper surface of the unit. After that, an upper pressing member is disposed on this cushion member. Then, the bottom-receiving member and the upper pressing member are fastened with a predetermined binding unit.
In such a housing unit, the glass plates piled up between the bottom-receiving member and the upper pressing member are fastened with the predetermined binding unit. Thus, the glass plates can be housed without the load shift. However, if the target to be housed is not the transparent glass plate having the resin frame but an opaque or semi-transparent rectangular thin panel without a frame, the technical problems as follows are found when the panel is housed.
First, the positioning of the cushion spacer on the thin panel is difficult.
More specifically, the cushion spacer is disposed on the upper surface of the glass plate at each of the four corners of the rectangle with a predetermined space from each other via the self-adhesive member. However, at each of the four corners of the rectangle, the cushion spacers are necessarily piped up in a columnar shape, while the glass plate is interposed between the cushion spacers. If the glass plate is transparent, the position of the cushion spacer positioned below the glass plate can be observed through the glass plate. Therefore, it is easy to pile up the cushion spacers in the columnar shape. In the case of an opaque or semi-transparent rectangular thin panel, however, it is difficult to position the next cushion spacer via the rectangular thin panel right above the cushion spacer below the rectangular thin panel. In this case, therefore, as the number of rectangular thin panels to be piled up increases, the cushion spacer to be adjacent thereto vertically is displaced. As a result, the risk of the load shift is increased. In particular, the load shift is more likely to be caused if the displacement occurs in a direction where the size of the rectangle formed by four cushion spacers becomes smaller.
Second, it is difficult to pile up or unload the thin panels efficiently. More specifically, four cushion spacers are needed to pile up one glass plate. The cushion spacers need to be positioned at predetermined positions of the glass substrate. In the case of piling up the rectangular thin panels without frames, the sides of the rectangular thin panels piled up are exposed. Therefore, the piling up requires extra attention. Thus, efficient piling up is difficult. This similarly applies when the piled thin panels are unloaded.    Patent Document 1: JP-A-2006-32978    Patent Document 2: JP-A-2003-200962